Method for producing polyarylene sulfide resin

Abstract

To provide a production method of a polyarylene sulfide (PAS) resin which recycles, as a polymerization material of the PS resin, a PAS oligomer generated by polymerization reaction of a PAS resin.SOLUTION: There is provided a production method of a PAS resin which includes the steps of: reacting, in an organic polar solvent, a polyhalo aromatic compound with a sulfidizing agent to obtain a crude reaction mixture; removing a solid-phase component from the crude reaction mixture through solid-liquid separation to obtain a liquid-phase component (A) containing at least a cyclic PAS oligomer and a chain PAS oligomer; supplying the liquid-phase component (A) into an evaporator, and concentrating the liquid-phase component at 230°C or lower under a reduced pressure or normal pressure environment, to obtain a mixture (B); supplying the mixture (B) into a reaction container; supplying a polyhalo organic compound, a sulfidizing agent and an organic polar solvent into the reaction container; and performing polymerization reaction in the reaction container, wherein a ring opening rate of the cyclic PAS oligomer in concentration is less than 10%.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing a polyarylene sulfide resin in which the ring-opening rate of a cyclic polyarylene sulfide oligomer contained in an organic polar solvent filtered in the production process of a polyarylene sulfide resin is controlled and concentrated, and the concentrated oligomer is reused as a raw material.

Background Art

[0002] Polyarylene sulfide (hereinafter sometimes abbreviated as PAS) resins typified by polyphenylene sulfide (hereinafter sometimes abbreviated as PPS) resins are excellent in heat resistance, chemical resistance, etc., and are widely used in applications such as electric and electronic parts, automotive parts, hot water supply machine parts, fibers, and films.

[0003] PPS resins are obtained by a method such as polymerizing a sulfidizing agent and a polyhaloaromatic compound in a polar organic solvent such as N-methyl-2-pyrrolidone (NMP). At this time, by-products such as PPS oligomers, residual sulfidizing agents, and sodium chloride are also generated simultaneously. These by-products are regarded as impurities and have not been actively utilized in the past. In particular, most of the PPS oligomers contained in the liquid phase component obtained by solid-liquid separation of the solvent slurry after polymerization are discarded as industrial waste, causing a great loss in production in terms of raw material cost loss and disposal cost.

[0004] Heretofore, a method for recovering the above liquid phase component as a polymerization raw material has been disclosed (see Patent Document 1). However, impurities (such as phenol) other than the PPS oligomers present in the liquid phase component inhibit the polymerization reaction, so the reuse rate as a raw material has been limited.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] Therefore, the problem that the present invention aims to solve is to provide a method for producing PAS resin in which a cyclic PAS oligomer obtained by solid-liquid separation of the crude reaction mixture after the polymerization reaction of PAS resin is reused as a polymerization raw material for PAS resin, thereby improving the reuse rate of the oligomer and providing a method to reduce loss. [Means for solving the problem]

[0007] As a result of various studies, the inventors of the present invention have found that by separating the reaction mixture obtained after the polymerization reaction of PAS resin from solid-liquid, and concentrating the liquid phase component obtained under reduced pressure or atmospheric pressure at 230°C or below, the ring-opening rate of the cyclic PAS oligomer can be controlled to less than 10% while removing polymerization-inhibiting impurities contained in the liquid phase component, and that by using a composition containing the PAS oligomer as a polymerization raw material for PAS resin, the PAS oligomer can be recovered with high efficiency, thus completing the present invention.

[0008] In other words, the present invention comprises the steps of: (1) reacting a polyhalo-aromatic compound with (i) an alkali metal sulfide or (ii) an alkali metal hydroxide and an alkali metal hydroxide in an organic polar solvent to obtain a crude reaction mixture containing at least a PAS resin, a cyclic PAS oligomer, a linear PAS oligomer, an alkali metal halide, and an organic polar solvent; (2) removing the solid phase component from the crude reaction mixture by solid-liquid separation to obtain a liquid phase component (A) containing at least a cyclic PAS oligomer and a linear PAS oligomer; (3) supplying the liquid phase component (A) into an evaporator and concentrating it at 230°C or below under reduced pressure or atmospheric pressure to obtain a PAS oligomer mixture (B); and supplying the PAS oligomer mixture obtained in step (3) into a reaction vessel. The present invention relates to a method for producing a PAS oligomer mixture, comprising the steps of: (4) supplying a compound (B); (5) supplying at least a polyhalo-aromatic compound, (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and alkali metal hydroxide, and an organic polar solvent into a reaction vessel; and (6) carrying out a polymerization reaction in an organic polar solvent in the reaction vessel obtained through steps (4) and (5), using at least a polyhalo-aromatic compound, the PAS oligomer mixture (B), and (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and alkali metal hydroxide as raw materials, wherein the ring-opening rate of the cyclic PAS oligomer at the time of concentration in step (3) is less than 10%.

[0009] In this invention, polymer compounds having 2 to 40 repeating units (a mixture of dimers to 40mers) may be referred to as "oligomers." [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a method for producing PAS resin by concentrating the cyclic PAS oligomer filtered off after the polymerization reaction of PAS resin while controlling the ring-opening rate, and recovering the resulting PAS oligomer mixture with high efficiency as a raw material. [Modes for carrying out the invention]

[0011] Hereinafter, an embodiment of the present invention will be described in detail. However, the scope of the present invention is not limited to the embodiment described here, and various modifications can be made without departing from the spirit of the present invention. Also, when a plurality of upper limit values and lower limit values are described for specific parameters, any upper limit value and lower limit value can be combined to form a suitable numerical range.

[0012] <Production method of PAS resin> The present invention involves reacting a polyhaloaromatic compound with (i) an alkali metal sulfide or (ii) an alkali metal hydrosulfide and an alkali metal hydroxide in an organic polar solvent to obtain a crude reaction mixture containing at least a PAS resin, a cyclic PAS oligomer, a linear PAS oligomer, an alkali metal halide, and an organic polar solvent (step 1); removing the solid-phase components from the crude reaction mixture by solid-liquid separation to obtain a liquid-phase component (A) containing at least a cyclic PAS oligomer and a linear PAS oligomer (step 2); supplying the liquid-phase component (A) into an evaporator and concentrating it at 230 °C or lower under reduced pressure or normal pressure to obtain a PAS oligomer mixture (B) (step 3); supplying the PAS oligomer mixture (B) obtained in step (3) into a reaction vessel (step 4); supplying at least a polyhaloaromatic compound, (i) an alkali metal sulfide, or (ii) an alkali metal hydrosulfide and an alkali metal hydroxide, and an organic polar solvent into the reaction vessel (step 5); and carrying out a polymerization reaction in the reaction vessel obtained through steps (4) and (5) using at least a polyhaloaromatic compound, the PAS oligomer mixture (B), and (i) an alkali metal sulfide or (ii) an alkali metal hydrosulfide and an alkali metal hydroxide as raw materials in an organic polar solvent (step 6). The following will be described in detail.

[0013] Step (1) Step (1) is a step of reacting a polyhalo-aromatic compound with (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide in an organic polar solvent to obtain a crude reaction mixture containing at least a PAS resin, a cyclic PAS oligomer, a linear PAS oligomer, an alkali metal halide, and an organic polar solvent.

[0014] The mixture used in step (1) is not particularly limited as long as it contains at least a PAS resin, a cyclic PAS oligomer, a linear PAS oligomer, an alkali metal halide, and an organic polar solvent, but it is preferable to use the crude reaction mixture obtained in the method for producing the PAS resin in step (6).

[0015] Process (2) Step (2) is a step of removing the solid phase component from the crude reaction mixture by solid-liquid separation to obtain a liquid phase component (A) containing at least a cyclic PAS oligomer and a linear PAS oligomer.

[0016] There are two main types of solid-liquid separation: the flash method and the quench method, which will be described later. The flash method is a method of recovering the solvent by evaporating it from the crude reaction mixture, and simultaneously recovering the solid material. Generally, the crude reaction mixture is flashed from a high-temperature, high-pressure state to an atmosphere of normal pressure or reduced pressure, and the solvent is removed and recovered while the solid material containing the PAS resin is recovered in powder form. A preferred embodiment of the flash method is a method in which the polymer reaction product obtained in the polymerization step, which is at high temperature and high pressure (usually 250°C or higher, 0.8 MPa or higher), is ejected from a nozzle into an atmosphere of nitrogen or water vapor at normal pressure. In the flash method, the solvent can be efficiently recovered by utilizing the heat of vaporization of the solvent when the polymer reaction product is flashed from a high-temperature, high-pressure state to a normal pressure state. The higher the internal temperature during flashing, the more efficient the solvent recovery becomes and the better the productivity. Therefore, the temperature and pressure inside the polymerization system during flashing are usually set to 250°C or higher, preferably in the temperature range of 255 to 280°C and 0.8 MPa or higher, preferably in the pressure range of 1.0 to 5.0 MPa. When flashing under reduced pressure or atmospheric pressure from this state, the ambient temperature is usually in the range of 150-250°C. If solvent recovery from the crude reaction mixture is insufficient, heating may be continued in an atmosphere of 150-250°C after flashing.

[0017] On the other hand, the Quench method is a method for recovering particulate PAS resin by slowly cooling the crude reaction mixture. Generally, the crude reaction mixture is gradually cooled from a high-temperature, high-pressure state to crystallize the PAS resin in the reaction system, and then the solid component containing the PAS resin is recovered as granules by solid-liquid separation using filtration or the like. There are no particular restrictions on the cooling time, but it is usually in the range of 0.1°C / min to 3°C / min. Furthermore, it is not necessary to cool at the same rate throughout the entire slow cooling process. It is also preferable to cool at a rate of 0.1°C / min to 1°C / min until the granular PAS resin crystallizes, and then cool at a rate of 1°C / min or higher. Finally, it is preferable to cool to 70°C or higher, preferably 100°C or higher and 200°C or lower, and then recover the solid component containing the polyarylene sulfide resin by solid-liquid separation. In the Quench process, solid-liquid separation can be performed by methods such as separating the material using filtration or a centrifuge such as a screw decanter, then adding water directly to the resulting filtration residue to form a slurry, and repeating the solid-liquid separation; or by heating the resulting filtration residue in a non-oxidizing atmosphere to remove any remaining solvent. The Quench process is preferred in this step because it is less likely to incorporate impurities such as by-products and unreacted raw materials into the polymer particles during crystallization, and a larger amount of PAS oligomer can be recovered.

[0018] Process (3) Step (3) is a step of supplying the liquid phase component (A) into an evaporator and concentrating the liquid phase component (A) at 230°C or below under reduced pressure or atmospheric pressure to obtain a PAS oligomer mixture (B).

[0019] The evaporator used in this process is made of a material resistant to organic polar solvents and is not particularly limited as long as it is a container that can be heated and depressurized. Known types can be used, such as evaporators, autoclaves, and thin-film evaporators.

[0020] When concentrating the liquid-phase component (A), the temperature in the evaporator is preferably 230°C or lower. Also, the pressure in the evaporator is preferably normal pressure or lower, specifically preferably in the range of 10 to 760 mmHg. By concentrating under such conditions, the ring-opening rate of the cyclic PAS oligomer can be controlled to less than 10%. The ring-opening rate is represented by the following formula. Ring-opening rate (%) = {1 - (weight fraction of cyclic PAS oligomer with respect to the PAS oligomer contained in the PAS oligomer mixture (B)) / (weight fraction of cyclic PAS oligomer with respect to the PAS oligomer contained in the liquid-phase component (A))} × 100

[0021] Also, when concentrating the liquid-phase component (A), it is desirable to adjust the amount of solvent removed so that the proportion of solids (non-volatile components) contained in the PAS oligomer mixture (B) is in the range of 20 to 100% by mass, preferably 20 to 99.99% by mass, and more preferably in the range of 30 to 90% by mass.

[0022] Also, when concentrating the liquid-phase component (A), since the volatile substances contained in the PAS oligomer mixture (B) are removed together with the organic polar solvent, impurities can be reduced. Examples of impurities include phenol and the like by-produced in step (1) and the sulfiding agent which is an unreacted raw material.

[0023] The cyclic PAS oligomer becomes a chain-like PAS oligomer having an active terminal such as a SH group when it is ring-opened by heat or the like. When this chain-like PAS oligomer is added to the PAS resin, the chain-like PAS oligomer promotes a nucleophilic attack on the sulfide site of the PAS resin during melting, etc., which causes a decrease in melt stability. In the present invention, by controlling the ring-opening rate of the cyclic PAS oligomer to less than 10%, it is possible to suppress a decrease in the thermal stability of the PAS resin due to the chain-like PAS oligomer.

[0024] The liquid phase component (A) obtained in this process may be temporarily stored in a container. When temporarily stored in a container, since the organic polar solvent immediately after the solid-liquid separation process is at a temperature higher than room temperature, the organic polar solvent, PAS oligomer, and other by-products may be oxidized more than necessary by oxygen in the air. This may cause polymerization inhibition when used (reused) in the subsequent polymerization reaction of the PAS resin. Furthermore, due to issues such as bumping or the working environment, the contents may be scattered outside the container. Therefore, it is preferable to seal the container using a container equipped with a sealing mechanism. Examples of sealing mechanisms include tension-tightening type locking mechanisms.

[0025] Process (4) Step (4) is the step of supplying the PAS oligomer mixture (B) obtained in step (3) into the reaction vessel.

[0026] The PAS oligomer mixture (B) obtained in step (3) may be supplied directly from the evaporator in step (3), or it may be temporarily placed in another container, removed from that container, and transferred to the reaction vessel for use.

[0027] The amount of PAS oligomer mixture (B) supplied in this process is not particularly limited, but it is preferable to adjust the amount of PAS oligomer contained in the PAS oligomer mixture (B) to be 0.1% by mass or more, more preferably 10% by mass or less, more preferably 7.0% by mass or less, and even more preferably 5.0% by mass or less, relative to the theoretical yield of PAS resin obtained from the subsequent polymerization reaction. Within this range, PAS oligomer can be recovered into the product while suppressing inhibition of the polymerization reaction by the PAS oligomer mixture.

[0028] Process (5) Step (5) is the step of supplying at least a polyhalo-aromatic compound, (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide, and an organic polar solvent to the reaction vessel to which the PAS oligomer mixture (B) obtained in step (3) was supplied. Steps (4) and (5) may be performed either first or simultaneously.

[0029] Here, the polyhalo-aromatic compounds in the present invention are, for example, halogenated aromatic compounds having two or more halogen atoms directly bonded to an aromatic ring. Specifically, examples include dihalo-aromatic compounds such as p-dichlorobenzene, o-dichlorobenzene, m-dichlorobenzene, trichlorobenzene, tetrachlorobenzene, dibrombenzene, diiodobenzene, tribrombenzene, dibromnaphthalene, triiodobenzene, dichlorodiphenylbenzene, dibromdiphenylbenzene, dichlorobenzophenone, dibrombenzophenone, dichlorodiphenyl ether, dibromdiphenyl ether, dichlorodiphenyl sulfide, dibromdiphenyl sulfide, dichlorobiphenyl, and dibrombiphenyl, as well as mixtures thereof. These compounds may be block copolymerized. Among these, dihalogenated benzenes are preferred, and those containing 80 mol% or more of p-dichlorobenzene are particularly preferred. Furthermore, in order to increase the viscosity of the PAS resin by creating a branched structure, polyhalo-aromatic compounds having three or more halogen substituents in one molecule may be used as branching agents as desired. Examples of such polyhalo-aromatic compounds include 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene, and 1,4,6-trichloronaphthalene. Furthermore, examples include polyhalo-aromatic compounds having functional groups with active hydrogens such as amino groups, thiol groups, and hydroxyl groups. Specifically, these include dihaloanilines such as 2,6-dichloroaniline, 2,5-dichloroaniline, 2,4-dichloroaniline, and 2,3-dichloroaniline; trihaloanilines such as 2,3,4-trichloroaniline, 2,3,5-trichloroaniline, 2,4,6-trichloroaniline, and 3,4,5-trichloroaniline; dihaloaminodiphenyl ethers such as 2,2'-diamino-4,4'-dichlorodiphenyl ether and 2,4'-diamino-2',4-dichlorodiphenyl ether, and compounds in which the amino group is replaced with a thiol group or a hydroxyl group in mixtures thereof.Furthermore, active hydrogen-containing polyhalo-aromatic compounds can also be used in which the hydrogen atoms bonded to the carbon atoms forming the aromatic ring in these active hydrogen-containing polyhalo-aromatic compounds are substituted with other inert groups, such as hydrocarbon groups like alkyl groups.

[0030] Among these various active hydrogen-containing polyhalo-aromatic compounds, the preferred is an active hydrogen-containing dihalo-aromatic compound, and the most preferred is dichloroaniline.

[0031] Examples of polyhaloaromatic compounds having a nitro group include mono- or dihalonitrobenzenes such as 2,4-dinitrochlorobenzene and 2,5-dichloronitrobenzene; dihalonitrodiphenyl ethers such as 2-nitro-4,4'-dichlorodiphenyl ether; dihalonitrodiphenyl sulfones such as 3,3'-dinitro-4,4'-dichlorodiphenyl sulfone; mono- or dihalonitropyridines such as 2,5-dichloro-3-nitropyridine and 2-chlor-3,5-dinitropyridine; and various dihalonitronaphthalenes.

[0032] Furthermore, in the present invention, alkali metal sulfides or alkali hydrosulfides and alkali metal hydroxides (hereinafter sometimes referred to as sulfidating agents) are used as raw materials.

[0033] In the present invention, the alkali metal sulfide includes lithium sulfide, sodium sulfide, rubidium sulfide, cesium sulfide, and mixtures thereof. Such alkali metal sulfides can be used as hydrates, aqueous mixtures, or anhydrous forms. Alkali metal sulfides can also be obtained by the reaction of alkali metal hydroxides with alkali metal hydroxides. In addition, it is acceptable to add a small amount of alkali metal hydroxide to react with the alkali metal hydroxides and alkali metal thiosulfates that are usually present in trace amounts in the alkali metal sulfides.

[0034] Furthermore, the alkali metal hydrosulfides include lithium hydrogen sulfide, sodium hydrogen sulfide, rubidium hydrogen sulfide, cesium hydrogen sulfide, and mixtures thereof. Such alkali metal hydrosulfides can be used as hydrates, aqueous mixtures, or anhydrous products.

[0035] Furthermore, the alkali metal hydroxide is used together with an alkali metal hydroxide. Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide, which may be used individually or in combination of two or more. Among these, lithium hydroxide, sodium hydroxide, and potassium hydroxide are preferred due to their availability, with sodium hydroxide being particularly preferred.

[0036] The present invention's method for producing PAS resin can also use a hydrated sulfidating agent as a raw material. In this case, it is preferable to dehydrate the hydrated sulfidating agent in the presence of at least an aprotic polar solvent before subjecting it to the polymerization reaction of the PAS resin. Furthermore, if the amount of aprotic polar solvent charged is small, for example, less than 1 mole per mole of sulfur atoms in the sulfidating agent, it is preferable to dehydrate the hydrated sulfidating agent and the aprotic polar solvent in the presence of a polyhalo-aromatic compound.

[0037] The dehydration step of the hydrated sulfidating agent is carried out by charging at least an aprotic polar solvent and a hydrated alkali metal sulfide or hydrated alkaline aqueous sulfide and alkali metal hydroxide as the hydrated sulfidating agent into a reaction vessel equipped with a distillation apparatus, heating to a temperature at which water is removed by azeotropy, specifically in the range of 300°C or less, preferably in the range of 80 to 220°C, more preferably in the range of 100 to 200°C, and then discharging the water from the system by distillation. In the dehydration step, it is preferable to dehydrate until the amount of water in the system carrying out the polymerization reaction is 5 moles or less, more preferably in the range of 0.01 to 2.0 moles, per mole of sulfur atoms of the sulfidating agent.

[0038] In addition, examples of organic polar solvents in the present invention include amides, ureas and lactams such as formamide, acetamide, N-methylformamide, N,N-dimethylacetamide, tetramethylurea, N-methyl-2-pyrrolidone, 2-pyrrolidone, N-methyl-ε-caprolactam, ε-caprolactam, hexamethylphosphoramide, N-dimethylpropyleneurea, and 1,3-dimethyl-2-imidazolidinonic acid; sulfolanes such as sulfolane and dimethylsulfolane; nitriles such as benzonitrile; ketones such as methylphenyl ketone and mixtures thereof. Among these, amides having an aliphatic cyclic structure such as N-methyl-2-pyrrolidone, 2-pyrrolidone, N-methyl-ε-caprolactam, ε-caprolactam, hexamethylphosphoramide, N-dimethylpropyleneurea, and 1,3-dimethyl-2-imidazolidinonic acid are preferred, and N-methyl-2-pyrrolidone is even more preferred.

[0039] Process (6) Step (6) is a step in which, in a reaction vessel obtained through steps (4) and (5), at least a polyhalo-aromatic compound and a PAS oligomer mixture are polymerized in an organic polar solvent using (B), (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide as raw materials. After the polymerization reaction in step (6), necessary post-treatment steps such as solid-liquid separation and washing can be performed to produce PAS resin.

[0040] In the PAS polymerization process, the polymerization reaction of the PAS resin is carried out by reacting the above-mentioned alkali metal sulfide as a sulfidating agent with a polyhalo-aromatic compound in the presence of an organic polar solvent. Alternatively, the polymerization reaction of the PAS resin is carried out by reacting the above-mentioned alkali metal hydroxide and alkali metal hydroxide as sulfidating agents with a polyhalo-aromatic compound in the presence of these organic polar solvents. The polymerization conditions are generally in the temperature range of 200 to 330°C, and the pressure should be in a range that substantially maintains the polymerization solvent and the polyhalo-aromatic compound, which is the polymerization monomer, in the liquid phase, and is generally selected from the range of 0.1 to 20 MPa, preferably from 0.1 to 2 MPa. The amount of polyhalo-aromatic compound to be charged is prepared in the range of 0.2 moles to 5.0 moles, preferably from 0.8 to 1.3 moles, and more preferably from 0.9 to 1.1 moles, per mole of sulfur atoms of the sulfidating agent. Furthermore, the amount of aprotic polar solvent charged is adjusted to be in the range of 1.0 to 6.0 moles, preferably 2.5 to 4.5 moles, per mole of sulfur atoms of the sulfidating agent. The polymerization reaction is preferably carried out in the presence of a small amount of water, and the proportion is preferably adjusted as appropriate in consideration of the polymerization method, the molecular weight of the obtained polymer, and productivity. Specifically, the dehydration operation is carried out so that the amount of water is in the range of 2.0 moles or less, preferably 1.6 moles or less, per mole of sulfur atoms of the sulfidating agent. However, if the dehydration operation is carried out in the presence of a polyhalo-aromatic compound (for example, the method in "5)" in the specific embodiment below), the amount of water should be in the range of 0.9 moles or less, preferably 0.05 to 0.3 moles, more preferably 0.01 to 0.02 moles or less.

[0041] Specific embodiments of polymerizing a sulfidating agent and a polyhalo-aromatic compound in the presence of the aforementioned aprotic polar solvent include, for example, 1) A method using polymerization aids such as alkali metal carboxylates or lithium halides. 2) A method using branching agents such as aromatic polyhalogen compounds, 3) A method in which polymerization is carried out in the presence of a small amount of water, and then water is added to further polymerize the molecule. 4) A method in which, during the reaction of an alkali metal sulfide with an aromatic dihalogen compound, the gas phase portion of the reaction vessel is cooled to condense a portion of the gas phase inside the reaction vessel and reflux it into the liquid phase. 5) A method for producing PAS resin, which includes the essential steps of: producing a slurry containing solid alkali metal sulfide by reacting an alkali metal sulfide, or a hydrated alkali metal hydroxide and alkali metal hydroxide, with an amide, urea, or lactam having an aliphatic cyclic structure while dehydrating it in the presence of a polyhalo-aromatic compound; further dehydrating the slurry by adding a polar organic solvent such as NMP and distilling off the water; and then polymerizing the slurry obtained through the dehydration step by reacting a polyhalo-aromatic compound, an alkali metal hydroxide, and an alkali metal salt of the hydrolysis product of the amide, urea, or lactam having an aliphatic cyclic structure, at a rate of 0.02 moles or less of water present in the reaction system per mole of a polar organic solvent such as NMP.

[0042] Thus, by polymerizing a dihalo-aromatic compound, a PAS oligomer mixture (B), and (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide in an organic polar solvent, a PAS resin is obtained as the product. In addition, cyclic PAS oligomers and chain-like PAS oligomers are also produced as by-products. Substances contained after the reaction may also include by-products such as alkali metal-containing inorganic salts, carboxyalkylamino group-containing compounds, and terminal SH group-containing compounds, as well as unreacted raw materials and water.

[0043] The post-processing steps required to produce the PAS resin are not particularly limited, but for example, (a) after the polymerization reaction is complete, the reaction mixture is first used as is, or an acid or base is added, and the solvent is removed under reduced pressure or atmospheric pressure, and then the solid after solvent removal is washed once or twice or more with a solvent such as water, the reaction solvent (or an organic solvent having equivalent solubility to the low molecular weight polymer), acetone, methyl ethyl ketone, or alcohols, and then neutralized, washed with water, filtered and dried, or (b) after the polymerization reaction is complete, the reaction mixture is mixed with a solvent such as water, acetone, methyl ethyl ketone, alcohols, ethers, halogenated hydrocarbons, aromatic hydrocarbons, or aliphatic hydrocarbons (solubilable to the polymerization solvent used and at least poor solvent for PAS). (c) After the polymerization reaction is complete, the reaction mixture is mixed with a reaction solvent (or an organic solvent having equivalent solubility to the low molecular weight polymer) and stirred, filtered to remove the low molecular weight polymer, washed once or twice or more with a solvent such as water, acetone, methyl ethyl ketone, or alcohols, then neutralized, washed with water, filtered, and dried. (d) After the polymerization reaction is complete, the reaction mixture is mixed with water, washed with water, filtered, and if necessary, acid is added during the water washing for acid treatment, followed by drying. (e) After the polymerization reaction is complete, the reaction mixture is filtered, washed once or twice or more with the reaction solvent as necessary, and then washed with water, filtered, and dried.

[0044] In addition, in the post-processing methods exemplified in (a) to (e) above, the drying of the PAS resin may be carried out in a vacuum, in air, or in an inert gas atmosphere such as nitrogen. The PAS resin can also be prepared in powder or granular form.

[0045] <Composition / Applications, etc.> The PAS resin obtained by the above manufacturing method may contain additives such as mold release agents, colorants, heat stabilizers, UV stabilizers, foaming agents, rust inhibitors, flame retardants, lubricants, coupling agents, and fillers, as long as they do not impair the effects of the present invention. As fillers, known and conventional materials may be used as long as they do not impair the effects of the present invention. Examples include inorganic fillers of various shapes, such as fibrous materials and non-fibrous materials such as granular or plate-shaped materials. Specifically, fibrous fillers such as glass fibers, carbon fibers, silane glass fibers, ceramic fibers, aramid fibers, metal fibers, potassium titanate, silicon carbide, calcium silicate, wollastonite, and other fibers and natural fibers can be used. Non-fibrous fillers such as glass beads, glass flakes, barium sulfate, clay, pyrophyllite, bentonite, sericite, mica, talc, attapulgite, ferrite, calcium silicate, calcium carbonate, glass beads, zeolite, milled fiber, and calcium sulfate can also be used.

[0046] The PAS resin obtained by the above manufacturing method can also be used by mixing it with the following synthetic resins and elastomers, to the extent that the effects of the present invention are not impaired. Examples of these synthetic resins include polyester, polyamide, polyimide, polyetherimide, polycarbonate, polyphenylene ether, polysulfone, polyethersulfone, polyetheretherketone, polyetherketone, polyarylene, polyethylene, polypropylene, polytetrafluoroethylene, polydifluoroethylene, polystyrene, ABS resin, epoxy resin, silicone resin, phenolic resin, urethane resin, liquid crystal polymer, etc. Examples of elastomers include polyolefin rubber, fluororubber, silicone rubber, etc.

[0047] Furthermore, the PAS resin of the present invention exhibits excellent heat resistance, moldability, and dimensional stability when subjected to various melting processes such as injection molding, extrusion molding, compression molding, and blow molding. For this reason, it can be widely used as, for example, electrical and electronic components such as connectors, printed circuit boards, and encapsulated molded products; automotive parts such as lamp reflectors and various electrical components; interior materials for various buildings, aircraft, and automobiles; injection-molded and compression-molded products such as precision parts such as OA equipment parts, camera parts, and watch parts; or extrusion-molded and pultruded products such as fibers, films, sheets, and pipes. [Examples]

[0048] The present invention will be specifically described below with reference to examples. These examples are illustrative and not limiting. Unless otherwise specified, "%" and "parts" refer to mass.

[0049] <Rating>

[0050] (1) Evaluation of phenol reduction rate by concentration of liquid phase components The phenol content of the liquid phase component containing PPS oligomers (hereinafter referred to as "NMP filtrate") and the concentrate of said filtrate (hereinafter referred to as "NMP filtrate concentrate") was measured by the following methods, and the phenol reduction rate due to concentration was calculated using the following formula. Phenol reduction rate (%) = {1 - (phenol content of NMP filtrate concentrate) ÷ (phenol content of NMP filtrate)} × 100 NMP filtrate Two g of NMP filtrate was placed in a lidded vial, and 0.1 g of monochlorobenzene and 8 g of acetone were added and the mixture was stirred. The amount of phenol in the supernatant of the resulting slurry was measured using a Shimadzu gas chromatograph, and the phenol content of the original NMP filtrate was calculated. • NMP filtrate concentrate 1 g of NMP filtrate concentrate and 10 g of water were separated into a lidded vial, and 5 M hydrochloric acid was slowly added dropwise under an ice bath to adjust the pH of the contents to 4 or less. Subsequently, 1 g of monochlorobenzene and 100 g of acetone were added and the mixture was stirred. The amount of phenol in the supernatant of the resulting slurry was measured using a Shimadzu gas chromatograph, and the phenol content of the original NMP filtrate concentrate was calculated.

[0051] (2) Evaluation of the ring-opening rate of PPS oligomers Water was added to both the NMP filtrate and the NMP filtrate concentrate to form aqueous slurries. Each aqueous slurry was subjected to solid-liquid separation, washing, and drying to obtain powders. 5.0000 g of the obtained powder was taken, 75 mL of chloroform was added, and the mixture was refluxed at 65°C for 1 hour. The residue after extraction was measured by weight as a chain-like PPS oligomer, and the solid contained in the obtained chloroform extract after slow cooling to room temperature was measured by weight as a cyclic PPS oligomer. The PPS oligomer content in the NMP filtrate and NMP filtrate concentrate was then calculated. From the obtained values, the ring-opening rate of the cyclic PPS oligomer in the NMP filtrate concentration process was calculated using the following formula. The results are shown in Table 1. W1 = Amount of cyclic PPS oligomer in 5g of PPS oligomer contained in NMP filtrate Amount of cyclic PPS oligomers in 5g of PPS oligomers contained in W2=NMP filtrate concentrate Ring opening rate (%)=(1-W2 / W1)×100

[0052] (3) Evaluation of melt viscosity and melt stability Using a Shimadzu CFT-500D flow tester, the temperature was set to 300°C and the load to 20 kgf / cm². 2 The melt viscosity was measured after holding for 6 minutes or 30 minutes at L / D = 10(mm) / 1(mm). Melt stability was compared using the viscosity change rate α. The viscosity change rate α was defined as follows: A smaller value of α indicates a smaller viscosity change rate of the resin and superior melt stability. Furthermore, V6 viscosity refers to the melt viscosity after holding for 6 minutes, and V30 viscosity refers to the melt viscosity after holding for 30 minutes. α = |{(V30-V6) / V6}| × 100

[0053] <Example 1> Process (1) A 150-liter autoclave equipped with a stirring blade and bottom valve, connected to a pressure gauge, thermometer, and condenser, was charged with 19.413 kg (150 moles) of flake sodium sulfide (60.3 wt% Na2S) and 45.0 kg (454 moles) of N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP). The mixture was heated to 209°C while stirring under a nitrogen stream, and 4.644 kg of water was distilled off (the remaining water content was 1.13 moles per mole of sodium sulfide). The autoclave was then sealed and cooled to 180°C, and 21.631 kg (147 moles) of p-dichlorobenzene (hereinafter abbreviated as p-DCB) and 18.0 kg (182 moles) of NMP were charged. At a liquid temperature of 150°C, the mixture was pressurized to a gauge pressure of 0.1 MPa using nitrogen gas, and the heating process was started. The liquid temperature was raised to 240°C over 135 minutes and held for 30 minutes. Then, the temperature was raised to 250°C over 40 minutes and held for 73 minutes to complete the reaction. After that, the autoclave was cooled.

[0054] Process (2) The bottom valve of the autoclave was opened at 100°C, and the reaction slurry was transferred to a 150-liter plate filter and pressure filtered at 120°C. 48.0 kg of NMP was added, and the mixture was pressure washed and filtered again. The recovered NMP filtrate (1) weighed 80.0 kg and contained 0.0190 kg of phenol and 1.09 kg of PPS oligomer (0.763 kg of cyclic oligomer and 0.328 kg of chain-like oligomer).

[0055] Process (3) The NMP filtrate was charged into an evaporator with a boiler wall temperature of 150°C, and NMP was removed by distillation under reduced pressure of 50 mmHg, yielding 3.78 kg of a brown solid residue with 45% by mass of non-volatile content. The residue contained 0.0010 kg of phenol, 0.763 kg of cyclic oligomers, and 0.328 kg of chain-like oligomers. The phenol reduction rate by concentration was 94.7%, and the ring-opening rate of cyclic oligomers was 0.00%.

[0056] Process (4) 0.802 kg of the brown residue obtained in process (3) was placed in a 150-liter autoclave equipped with a stirring blade and bottom valve, which was connected to a pressure gauge, thermometer, and condenser.

[0057] Process (5) 19.413 kg of flake sodium sulfide (60.3 wt% Na2S) and 45.0 kg of NMP were charged into the same autoclave. The mixture was heated to 209°C while stirring under a nitrogen stream, and 4.644 kg of water was distilled off (the remaining water content was 1.13 moles per mole of sodium sulfide). The autoclave was then sealed and cooled to 180°C, and 21.631 kg of p-DCB and 18.0 kg of NMP were charged. The amount of oligomer added in step (4) was 1.5 mass% of the theoretical yield of PPS resin in the subsequent polymerization reaction (step (6)).

[0058] Process (6) The autoclave was started by pressurizing the liquid at 150°C using nitrogen gas to a gauge pressure of 0.1 MPa and increasing the temperature. The liquid temperature was increased to 240°C over 135 minutes and held for 30 minutes. Then, the liquid temperature was increased to 250°C over 40 minutes and held for 73 minutes to complete the reaction. After that, it was cooled to 120°C over 3 hours to obtain a slurry. Next, 100.0 g of the obtained slurry was filtered (a Kiriyama funnel was lined with cellulose filter paper with retaining particles of 1 μm, the beaker containing the slurry was placed in a water bath, and after the slurry temperature reached 50°C, it was poured into the funnel and filtered under reduced pressure using a water pump) to remove the solvent. To dissolve the NMP and by-product sodium chloride remaining in the filtration residue, they were dispersed in 400 g of 60°C warm water and stirred for 10 minutes, then filtered again, and 400 g of 60°C warm water was passed through the filter cake. After repeating this operation three times, the water-filtered cake was dried in a hot air circulating dryer at 120°C for 3 hours to obtain powder (1).

[0059] <Example 2> In step (4), the process was carried out in the same manner as in Example 1, except that the amount of brown residue added was 1.60 kg, to obtain powder (2). The amount of oligomer added was 3.0% by mass relative to the theoretical yield of PPS resin.

[0060] <Example 3> In step (4), the process was carried out in the same manner as in Example 1, except that the amount of brown residue added was 2.67 kg, to obtain powder (3). The amount of oligomer added was 5.0% by mass relative to the theoretical yield of PPS resin.

[0061] <Example 4> In step (4), the process was carried out in the same manner as in Example 1, except that the amount of brown residue added was 3.74 kg, to obtain powder (4). The amount of oligomer added was 7.0% by mass relative to the theoretical yield of PPS resin.

[0062] <Example 5> In step (3), the NMP filtrate was concentrated at a can wall temperature of 210°C and atmospheric pressure. 3.78 kg of a brown solid residue with 45% non-volatile content was obtained. The residue contained 0.0006 kg of phenol, 0.760 kg of cyclic oligomers, and 0.331 kg of chain-like oligomers. The phenol reduction rate due to concentration was 96.8%, and the ring-opening rate of the cyclic oligomers was 0.39%. The rest of the procedure was the same as in Example 2 to obtain powder (5). The amount of added oligomer was 3.0% by mass relative to the PPS resin.

[0063] <Example 6> In step (3), the NMP filtrate was concentrated at a can wall temperature of 210°C under atmospheric pressure, and the procedure was carried out in the same manner as in Example 3 to obtain powder (6). The amount of oligomer added was 5.0% by mass relative to the PPS resin.

[0064] <Comparative Example 1> In step (3), the NMP filtrate was concentrated at a can wall temperature of 250°C and atmospheric pressure. 3.78 kg of a brown solid residue with 45% non-volatile content was obtained. The residue contained 0.0006 kg of phenol, 0.534 kg of cyclic oligomers, and 0.556 kg of chain-like oligomers. The phenol reduction rate due to concentration was 96.8%, and the ring-opening rate of the cyclic oligomers was 30.0%. The rest of the procedure was the same as in Example 2 to obtain powder (C1). The amount of added oligomer was 3.0% by mass relative to the PPS resin.

[0065] <Comparative Example 2> In step (3), the NMP filtrate was concentrated at a can wall temperature of 250°C under atmospheric pressure, and the procedure was carried out in the same manner as in Example 3 to obtain powder (C2). The amount of oligomer added was 5.0% by mass relative to the PPS resin.

[0066] <Comparative Example 3> In step (3), the NMP filtrate was concentrated at a can wall temperature of 270°C and atmospheric pressure. 3.78 kg of a brown solid residue with 45% by mass of non-volatile content was obtained. The residue contained 0.0005 kg of phenol, 0.311 kg of cyclic oligomers, and 0.780 kg of chain-like oligomers. The phenol reduction rate due to concentration was 97.3%, and the ring-opening rate of the cyclic oligomers was 59.3%. The rest of the procedure was the same as in Example 2 to obtain powder (C3). The amount of added oligomer was 3.0% by mass relative to the PPS resin.

[0067] <Comparative Example 4> In step (3), the NMP filtrate was concentrated at a can wall temperature of 270°C under atmospheric pressure, and the procedure was carried out in the same manner as in Example 3 to obtain powder (C4). The amount of oligomer added was 5.0% by mass relative to the PPS resin.

[0068] <Comparative Example 5> In Example 2, steps (3) and (4) were omitted, and in step (5), 34.1 kg of the 45.0 kg of NMP charged into the autoclave before dewatering was used as the NMP filtrate obtained in step (2). The rest of the procedure was the same as in Example 2 to obtain powder (C5). The amount of oligomer added was 3.0% by mass relative to the PPS resin.

[0069] <Reference example (1)> Steps (1) to (4) were omitted, and only steps (5) and (6) were performed in the same manner as in Example 1 to obtain powder (R1) with an oligomer addition rate of 0%.

[0070] [Table 1]

[0071] The results in Table 1 show that, compared to the comparative example, the V6 viscosity of the obtained PAS resin in the example was higher and the viscosity change rate was smaller. This indicates that oligomers can be recovered with high efficiency and PPS with excellent thermal stability can be obtained.

Claims

1. Step (1): A step in which a polyhalo-aromatic compound is reacted in an organic polar solvent with (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide to obtain a crude reaction mixture containing at least a polyarylene sulfide resin, a cyclic polyarylene sulfide oligomer, a linear polyarylene sulfide oligomer, an alkali metal halide, and an organic polar solvent. Step (2): Remove the solid phase component from the crude reaction mixture by solid-liquid separation to obtain a liquid phase component (A) containing at least a cyclic polyarylene sulfide oligomer and a linear polyarylene sulfide oligomer. Step (3): Supply the liquid phase component (A) into the evaporator and concentrate it at 230°C or below under reduced pressure or atmospheric pressure to obtain a polyarylene sulfide oligomer mixture (B). Step (4) involves supplying the polyarylene sulfide oligomer mixture (B) obtained in step (3) into the reaction vessel. Step (5) of supplying at least a polyhalo-aromatic compound, (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide, and an organic polar solvent into the reaction vessel, The process includes step (6), in which at least a polyhalo-aromatic compound, a polyarylene sulfide oligomer mixture (B), and (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide are polymerized in an organic polar solvent in a reaction vessel obtained through steps (4) and (5), and In step (3), the ring-opening rate of the cyclic polyarylene sulfide oligomer during concentration is less than 10%. The amount of polyarylene sulfide oligomer contained in the polyarylene sulfide oligomer mixture (B) supplied in step (4) is 0.1 to 10% by mass relative to the theoretical yield of PAS resin obtained in step (6). The ring opening rate is {1 - (weight fraction of cyclic polyarylene sulfide oligomer relative to polyarylene sulfide oligomer contained in polyarylene sulfide oligomer mixture (B)) / (weight fraction of cyclic polyarylene sulfide oligomer relative to polyarylene sulfide oligomer contained in liquid phase component (A))} × 100 A method for producing polyarylene sulfide resin, characterized by being calculated by [a specific method].

2. The method for producing a polyarylene sulfide resin according to claim 1, wherein the solid-liquid separation step (2) is a step using the Quench method.

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